Ghoul or Devil?
by apatheticwriterforfun
Summary: Issei, a ghoul. The lowest of the lows in the supernatural world, tortured and experimented on in his pursuit of power. But now, watch as he shakes the supernatural world to its core... IsseixOCxKoneko OPIssei Ghoul Issei
1. Prolouge: Ghoul

**AN: First Fanfiction, if you like it, favorite it, and leave a review, and I'll keep making these I guess.**

The never-ending thumping pain was much worse than anything else Issei had endured. Until now, his life had been full of jolts of pain, as he always lived as a bottom-feeder. He was a supernatural creature, but he was the lowest of the low. A ghoul.

Unlike the retarded myths and legends, ghouls never really ate humans and were actually quite peaceful by nature. Ghouls could eat human foods, and their only strong suit was their minorly enhanced physical abilities and their one trait. That one trait was both their only power and their crippling weakness.

Ghouls could and needed to suck the life out of humans. Other supernatural creatures worked too, but humans were the only real creatures a ghoul would even have a chance against in a one on one confrontation.

While ghouls do take life away from humans, almost all of them prefer to do it to asleep humans, and take a few months or years here and there, and try to live as normally as possible. After all, their enhanced abilities only allowed them to be slightly stronger, and any bodybuilder with armed humans would have a good chance of killing them.

The catch for ghouls was that they needed to do this by the time they were 13. All ghouls start off with 13 years of life. On there exact 13 birthday, if they hadn't stolen a life, their time would run out.

But a few select ghouls, like him, had realized something. If they killed a human, and then ate them, they would still receive all the life the human would have had, despite the fact he was dead. Not only that, but they would also get a little bit stronger each time.

However, he was the only ghoul that took this to an extraordinary level. He lusted for power. And he knew that humans would never satisfy the amount of power he would need. He wanted more. He needed more.

And so he committed the largest sin recognized by ghouls. He went after another supernatural creature. He planned to kill a devil.

At the time of his decision, he was still just 14.

~Line Break~

But of course, as previously stated, ghouls, even enhanced ghouls who ate humans, didn't have the power to take on devils. Not only did they lack the physical power, they also lacked access to any form of magic. But most importantly, they lacked knowledge.

Being the bottom-feeder of supernatural society, ghouls had always lived in the human world. They nearly never made contact with anything other than humans, and almost always die if they ever interacted with a devil or a fallen angel.

And so, as Issei headed on his quest to kill a devil, he never realized how doomed he was. Not about the obstacles like magic, or their society, or the different class systems. He assumed that these legendary "devils" were just stronger humans. From the relative ease of killing humans once his powers were enhanced, his confidence soared.

He followed every lead he could find, rumors, eyewitnesses. He followed the occult research groups. And here he finally was. He found the train station, in which he had heard devils could use to go to a secret layer. For the past few days he had been waiting in front of the elevator, seeing who goes in, holding a cross, and a bottle of supposed holy water he received from a kind priest he met on his search.

After days of this, avoiding security guards when they bothered him, he finally found a promising candidate. He was tall, with bright green hair, and glamorous clothing. When he say Issei, he seemed to hesitate for a second seeing the cross and water taking a step back, before hurriedly walking into the elevator.

While this was fairly normal behavior, Issei saw something hanging out of his pocket when stumbled back a step. A gold chain with the key of the house of Astaroth on it. Isseiumo promptly got up and followed the man into the elevator. Finally, his labors would bear fruit. He would comfort him in the elevator, then splash the holy water on him and stab him.

But of course, his plan failed. What would've been a somewhat feasible plan had he known the right information and stabbed him with a knife coated in holy water, he had not known about the devil's inhuman reflexes. The instant Issei took out the bottle, a magic circle was instantly drawn.

As the water splashed harmlessly off the circle, Issei's knife was knocked aside, and Issei himself was promptly knocked unconscious.

The devil smiled, as he thought about what to do next.

"Ah. And here I was surprised, thinking that a priest was after me. I am surprised though, that a little ghoul would dare come after a devil, much less a high classed devil like myself. But if it's power you desire, I shall grant it to you…"

~Line Break~

Issei's life was hell. He never had to worry about food, nor his survival. But since that day, he had been kept in a sealed room, with him given 2 meals a day, of just normal, human food. While it did nothing good for his sanity, the time he spent in his room was the best part of the day.

What he dreaded every day, was his "experimentation" sessions. 4 hours, on the dot, every single day. He would be stabbed with a needle and had a steroid function of sorts pumped into him. A mix of devil blood, and human blood. His body absorbs it, making him stronger, and over the months he had been here, he had undoubtedly gotten much much stronger.

But what he despised was what came after the injections. The "doctors" would do a series of the same checkups every single day. First was magic aptitude. Every day, without fail, he was forced to try to draw a magic circle and activate a spell. Any spell. A hundred times a day. Each time he couldn't they would have a different punishment. 100 volts of electricity. Being burnt with a flaming hot rod. Whipped with a barbed bullwhip. And for the past few months, he had not succeeded one time.

Second, was pain tolerance. This was beyond cruel psychological tests. Every day, he would be set on fire, at four hundred degrees Fahrenheit, and he had to endure. If he could go ten minutes without screaming, they healed him and promised he could skip the "experiments" the next day. He had never missed this. If he could go 10 minutes without pressing the button labeled escape, even if he screamed, he would be realized at the ten-minute mark and have the fire put out, and his body healed immediately. He had never missed this either. But if he did press the button and screamed, he would be let out, but have to endure the extra test.

The extra test. His healing factor. With the burns he would have suffered from the second experiment, he was forced to sit for an hour, waiting for the burns to heal. With his body receiving the devil's blood, the wounds would close fairly fast. But if he couldn't heal all of his wounds within the hour, they would force him to go into the last experiment with his wound.

The final test. The one that was utterly breaking for Issei. He was used to pain. Ghouls never lived easy lives, and since childhood, he had been living on the streets, as ghoul parents almost never kept their children. He had been burnt before, shocked before. But the physical test was torture for him.

He was forced into a cylindrical tube, where a 100 cubic foot sandstone boulder was dropped on him. With his newly enhanced body, these were possible. Hard as hell, but compared to the other tests, he was sure he could maIsseie this. But unlike the other tests, this one was not so much focused on his physical abilities, but much more on mental conditioning.

The lab that he was in, was a massive one. Full-on hundreds of test subjects his captor had somehow acquired, with more coming by the day. Full of random species, whether they be the lowest of the devils, ghouls, sometimes even humans. And for this last test, this was important.

Five randomly selected "subjects" were chosen. And their tunnels were linked. So if anyone dropped their boulder, it would fall onto the next person below them, after smashing the original carrier to a pulp.

This meant you were utterly relying on the person on top of you. Some days, you would get lucky and have someone insanely strong above you. But sometimes you had to hold out with multiple boulders because your luck of the draw was bad.

Despite this, Issei was determined. He was not going to let that insane bastard and his "research team" break him. He kept onto his sanity, day in and day out. Counting the seconds, daydreaming, writing poems in his head. Whatever it was, he did it. His determination lasted, and even in the months of him being in the hellhole, he never relented.

However, after close to a year had passed, his researchers started to ignore him. They didn't always bring him out for trials, and when they did, they did it half-heartedly. While this was a relief for Issei, his mind screamed as he realized all too late what it meant besides he immediately relief.

They no longer needed him.

At this point, he wouldn't have minded death so much. His life wasn't great as it was, and honestly, death was really inevitable as long as he remained here. And so he came to terms with the possibility of long ago.

Sadly, even after his spell of time in the facility, he naively still thought death and torture were the worst things to be able to befall him. Unbeknownst to him, the facility never just peacefully killed their subjects. After all, there were always chemical solutions and weapons to test.

One day, as he predicted, a guard told him his "final date" was to be 3 days later. No sympathy, no pity from the guard. This happened all too often.

But for this tragic life of his, the normal chemical or weapon experiments were far too mediocre. For our main character, there awaited nothing but the cruelest fate. One which freed him, but entrapped him in the world of the supernatural, putting him into the position of power he had always dreamt of. But good things always come as a cost and any luck experienced would always be paid back...


	2. Chapter 2

**AN: Ngl, I feel like this is becoming a bit intense, but I guess this is necessary for a story like this… I will admit though, this is showing some similarity to Tokyo Ghoul, kinda. I'll try to steer it away, if you guys think I should leave it be, or have some other opinion, leave a review or PM me, and I'll try/pretend to care. No, but seriously I'll try my best to make this original unless you guys have different opinions.**

The day had arrived. The day of reckoning, the day that Nagumi fooled himself he was fine with. He had accepted his fate, and he had been mentally composing fake wills, testaments that would go unheard.

Nagumi woke up that day to a standard breakfast, with a simple note for him to make peace. He assumed it meant death, so he ignored it.

But at noon, when he was brought into a facility and made to shower and be sterilized, he realized they didn't just want to end his life. Letting him die peacefully was far too much to expect out of a place like this at this point, he assumed.

The idea was further enforced when they strapped him to a table, with him being blindfolded and handcuffed.

"Why the hell can I being restrained? Don't you fuckers have the decency to at least a man die in peace?"

"Don't be so naive. Our personal motto at this facility is 'Waste Not Want Not" after all. Especially when it comes down to our subjects now."

"Don't you devils have even the slightest of restrictions on this lab? Is your race seriously this fucked up?"

"Ha! You thought this is a legal facility? This is a lab ran 'privately' by the Astaroth family. After all of those other devils became soft and wouldn't let us use kidnapping for subjects, we took things into our own hands."

"Just let me die… if you devils feel any empathy at all, please just let me die…"

"Of course we feel empathy. But a failure like you should be grateful. A being like you is receiving this treatment. A purebred ghoul should be just about able to absorb all of this... but unfortunately, we don't have any data for ghouls yet, hence why you're here."

Nagumi was panicking. His flimsy acceptance of death was fading fast, but he still would've preferred that cover whatever this "researcher" had in mind for him. He knew devils treated lesser species with little respect, but to be treated like a guinea pig, a sin beyond even devils was horrifying.

"Alright. We'll carry ahead now. Inject the devil blood into him. 8L, and bleed him out while doing it."

Nagumi raised his voice to object, but as he was, four more "researchers" appeared, and stabbed his body full of needs, hooked up to a plastic bag filled with blood.

"Arrgh! Jesus! Can't you at least give me some anesthetic?"

As he said, he saw the researchers flinch in pain. But his amusement was short-lived as they just stabbed more objects into him, these draining his blood.

"Hmm. Did we forget that now? Well, too late now, maybe you can endure it for a bit? We'll cycle the mix of devil and ghoul blood through you. Be in bliss now; the start is the easiest part."

The next hour was a mix of him passing from pain, before promptly getting work back up. Gradually the ghoul blood was filtered out, and they inserted the final ingredient, something that Nagumi had never expected to be in a lab like this.

"Be grateful child. You're receiving the blood of a dragon king. You have no idea how hard it was to convince Tannin to give us two liters of his blood. We had to promise him land and favors to test this on you."

This time, the three blood types coursing through him was far too powerful for his body to handful. As his body literally tore itself apart, the researchers came in with healers.

As his muscles and fat were torn apart only to be healed back, one part of him that never ceased to function was his mind. Through the pain and self-pity, he swore to himself. If he could escape, he would never again be trapped, forever choosing death over imprisonment. But even as he now wanted to die rather than suffer from the pain and humiliation at the hands of the researchers, death was no longer an option.

And so he sat there in abject horror, suffering for days. Never-ending, having dragon, devil, and ghoul blood cycled in and out. His luck came in terrible mistakes for the researchers, and a blind stroke of luck for him.

**~Line Break~**

Up until this fateful day for him, he had been fed human meat and blood at regular intervals, just enough to keep him alive and relatively healthy. But the researchers got tired of him, realizing he wasn't getting much stronger, only slowly deteriorating and wasting away.

So in a last-ditch attempt to get some sort of result out of him, before disposing of him once and for all, they thought 'Well, he was captured for wanting devil flesh to gain power. Why not try to give it to him?'. As they figured, no amount of a powerup could free him from layers of norse-enchanted steel and magic barriers as a ghoul.

Sadly for them, they never realized quite how mistaken they were. Ghouls had weak physical bodies, and no magic to speak of, yet that was because they were a different type of demon. Unlike devils, which evolved and chose raw power, they furthered the evolution in a different type. Supernatural Digestion. Rather than just sucking nutritions like every other lifeform, they chose an incredible ability to take power from what and who they ate. Useless on processed foods or livestock products, but when eating a human, they would get a slight advantage. Against a devil or angel, if they could get just one morsel of their flesh, they would be formidable.

Yet, what could have been a strong contender to devils and angels, was sadly shut down before they could truly effectively use their evolutionary powers. As God, a being that at the time no one but Ophis or Great Red, or perhaps a collection of the strongest of dragons, could challenge, made the Archangels, and Lucifer. They killed ghouls and protected their respective species, leading the secret of even digestion to be a folktale for the supernatural. No ghoul had tasted devil or angel flesh in the past two thousand years.

The trend was finally broken by the foolish, unregulated researchers who had not thought to consult anyone before feeding the corpse of a devil that had just been killed in trials to Nagumi. For the first, unprecedented time in recorded history, a ghoul had managed to eat a devil, in its whole. Sadly, even as Nagumi struggled with his newfound power, his researchers had been correct.

But they kept feeding him. They strayed from their original goal, as they gained a borderline possessed attitude about it. Would stronger devil meat work? Would even some low-quality dragon meat do anything?

Nagumi grew stronger by the day, and while still sedated, he slowly realized the previously unbreakable restraints were now easily shattered. But he waited. He knew that never again would he have such lucky circumstances as to be given what he had so desperately searched for. He had begun his journey to gain power, and now that he has been steadily supplied with it, he was content.

But slowly, the researchers regained their senses, realizing the power he was amassing, despite him trying to hide it. Slowly, the meat stopped coming, and tensions grew. Security was doubled, then tripled, and they planned a disposal date. But it was too late. No amount of middle-class devils could've stopped Nagumi at this point.

As they stopped feeding him, Nagumi knew the gig was up. It was time for him to escape. And so he snapped off the cuff he had struggled so much against just a few weeks earlier and set off on his crusade.

"Imprison me? Let's see how much blood must be spilled in exchange for all those months of despair."


	3. Chapter 3

**AN: I realized that my original plan of having Issei and Nagumi sort of overlap wouldn't work… so I decided to cut out Nagumi. On the bright side, 10 followers! Took me 6 months to get that in subscribers on youtube, so yay! Follow, Favorite, Review, it really helps my low self-esteem. Plus, it justifies me putting off my 4-page research paper to write fanfiction**

**To answer the question of whether this is still Issei or a new person, this is sort of both. Read on, and believe he won't be any less badass/OP.**

**PS: To the people who have moved over from my previous story, I might migrate it over to this account once this is over. I do still love that story, along with Rising Tides (though that will probably not get a migration)**

He was out. The researchers were calm at first, believing that the tens of mid-classed devils could subdue him. They were more worried about the chance of their lab being discovered than anything else.

But as he tore through the mid-classed devils, getting more powerful as he killed each and consumed them. The researchers safely barricaded themselves in a testing room, as they called for backup. For a minute, they thought they were safe, as the room had been built like a bunker, completely resistant to all but the strongest of magic.

Yet Issei tore through it. With pure brute strength, he grabbed ahold of the maraging steel wall and pulled some of the steel off. The researchers were in disbelief. Sure, it was still stuff that humans made, but it has a tensile strength of 2700 MPa (Around 391601.9 pounds of force per square inch. In context, a hippo's bite, the strongest in the animal kingdom, is around 1800).

Slowly, the steel was torn away as Issei drew closer. At the moment, he no longer cared about power. These people, who have exploited him, and tortured him almost just for pleasure, could finally see what the consequences were.

"Stop! We'll give you blood! And the latest supplements! You could double your strength! Spare us, and we'll make you undoubtedly the most powerful ghoul in existence!"

"No. I'm done with being your guinea pig. The only thing farther you could give me is your blood."

"Why! Just leave us. We'll give you anything. All your worldly desires, we can ask the Astaroth family to provi…"

"And here I was thinking guys like me and you understood each other. You used to hurt me in excess just for fun right? Now I'm doing the same. What's so weird about that?"

This was the point where Issei snapped. His link to sanity was finally destroyed. Only his base desires remained, **revenge and power**. As a supernatural being, the latter was born out of genetics, but the former was trained into him. Scientists always wondered what Pavlov's dogs would be like if you trained them to aggression rather than hunger. And Issei was trained to aggression.

After killing the few researchers in the facility, along with every guard who didn't activate a magic circle in time, he decided. After all the team tests, and him getting squashed for their incompetence, he concluded it was only fair for him to kill them in turn too.

Whether they were fellow ghouls, beasts, angels, fallen angels, devils, he killed them regardless, adding their strength and their skills (to an extent) to his ever-increasing arsenal. But he was never satisfied, moving on to the next quickly to try to put out the fire in him that burnt, and smoldered, but never stopped burning. And it wouldn't stop until it burnt through his entire being. A parasite, moving through him, though what happened later would make it smolder indefinitely, waiting to be reawakened.

A thought no logical being would have would drive him to the status of serial killer that day. So much so, that by the end of his killing (and feeding), he had killed hundreds. Some, hopelessly damaged, but some innocent and retrievable from the depths of depression and abuse.

But as he stepped into the second to last room, he saw a 14-year-old girl, with bright blonde hair dirtied by the prison cell and its filth. But what he truly noticed was her eyes, laced with the same edge of resignation that he had once had.

"...Even if you'll kill me, I must thank you for helping me in the end. Better to be killed quickly than the fate _they_ had in mind for me. All for being one of the last vampires… if I had reached maturity before you came."

Issei was read to slice the head off of this gibberish speaking girl. But then he heard a scream.

"No! Let her live! She was only trying to protect me! Kill me! Please! I won't resist if you just let her go!"

Issei turnt around, only to find a desperate looking, yet ever so frail boy struggling against the bars of his cell. He felt a surge of anger, equally because of the boy pleading with him, but also being reminded of his weak self before his "treatment".

"What? You won't resist? How the fuck could you? You don't have power. You don't have strength nor magic. I could kill you faster than you could respond. Why the hell are you here anyways?"

"I'm sorry! I beg you, please just spare her. Those men came for my gear or something, and Yue tried to help me! You can't kill her for that!"

Issei realized the boy was a Sacred Gear holder, probably a strong one. But he didn't care at the moment, as his head was in agony. His sane side, with sympathy, and empathy, the weak **human** traits that he had been determined to lose, came back and tore at him, screaming at him to see what he had become.

Yue, seeing the door was open, and her attacker more or less incapacitated, thought about running. But she knew even with her natural-born athleticism she would never escape and had no chance of fighting back. There were much stronger people trapped in this prison, in the same condition, and he had killed them. She hadn't even reached her full vampire maturity.

"Besides," she reasoned, "if I run now, Nagumi (the weak boy next door, for real this time) is dead for sure. Then I might as well have spent a month here for nothing."

After a minute of struggling, and his logical brain seeing Yue staying despite the open door, his sympathetic side won out. He would offer then both a chance.

"It will be a hard path. Others will not show us sympathy, and we cannot afford to trust anyone. I will not trust you until you have proven yourselves. The Astroth family will hunt me down, to the ends of the earth, even if the majority of devils will not. Would you really chose this life over the release of death?"

Nagumi, still the ever so naive human accepted instantly. But Yue was far more careful of his offer. If this stranger wanted her for the purpose she thought she had escaped, then she would choose death instantly. But, she still wanted to keep Nagumi alive, and the stranger still did seem to have empathy for them.

And so, ever so hesitant, she too accepted his offer.

There, the trio of ghoul, pre-developed vampire, and untrained sacred gear user banded together. Presently weak, but with possibly the most potential any group could hope to have, they would shake the supernatural world to its core. May the gods fear, for they would not accept their subjected fates.


	4. AN: Quick Question

**Sorry, I read fanfiction too, and I hate to read these "fake" chapters too, so I'll keep it short. I try ti out in half an hour every day in this, and though it may not reflect that, I do a shitload of drafting/planning before writing. I basically plan 2 chapters ahead and have people read it before. So, I was wondering if you as the audience, would like longer chapters or faster updates. The time spent will be the same. Yes... for the Heavenly Black Kitsune readers you might remember this but for reals this time. Leave a review or PM me your opinion. **

**PS: Why is it the story I wrote on a whim so popular with 40000 views and 200 followers, and this one progressing 23% slower? (Yes, I read the charts). So, offer! If you can get to these goals (25 followers-40 minutes a day, 50 followers- an hour a day). I won't open a or anything, but if you guys have opinions I'd love to hear them. I'll also try to answer questions, as long as they don't ask for spoilers. And... this is way too long I'll stop now.**


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